Grass mowing machines known as zero turning radius (“ZTR”) mowers have at least one independently powered drive wheel on each side of a frame. One drive wheel may be operated in a forward direction while the other drive wheel may be stopped or operated in reverse. Many ZTR mowers have a twin stick control system. A pair of control levers or sticks may be provided side-by-side, with each lever or stick controlling one of the drive wheels. When both levers or sticks are advanced together forwardly out of their neutral position, both drive wheels rotate forwardly to cause the mower to move forward. A ZTR mower may be steered by advancing one lever or stick more than the other.
Typically, each control lever or stick on a ZTR mower may be linked to a pump arm of one of two separate hydraulic pumps, or of a dual hydraulic pump; i.e., a separate pump for each wheel. The lever or stick may be used to move a pump swash plate through a direct linkage.
The dual lever steering controls may be mounted on a ZTR mower frame so that each has a first pivot axis allowing the lever or stick in the operating position to pivot forwardly in an arc to turn the wheel in forward, or pivot rearwardly to turn the wheel in reverse. Additionally, the operator can pivot each lever or stick to a neutral operating position, and then pivot each lever or stick outwardly in an arc to a non-operating or park position. However, if one lever or stick is pivoted forward and the other is at or near the neutral position, the ZTR mower's inner wheel has a tendency to damage the turf. During very short, small radius turns, the inside wheel that stops or turns very slowly may slide and scrape the grass where the inside wheel is positioned.
There is a need for a simple and inexpensive mechanism for dual lever steering controls on a ZTR mower that minimizes or eliminates turf damage during short, small radius turns. A need exists for a mechanism for a ZTR mower that does not slide or scrape the grass where the inside wheel is positioned during turns.